Hello
I have been working with JSON:API for a caching-heavy application & wondered if there’s any standard / discussion around including field-level expiry metadata in JSON:API responses. 
Right now, cache-control & ETags can manage whole-resource expiration but in many real-world APIs; certain attributes (like price, stock, or location) update more frequently than others. 
Embedding expiry metadata at the attribute level could help clients make smarter refresh / polling decisions.
I am aware this might go beyond the core spec but curious if anyone has tackled this use case. For eg; imagine a product API where the description rarely changes; but the price changes every 60 seconds sending a meta.expires_at per attribute could reduce unnecessary data fetches. 
I have not seen this discussed widely and wonder if it conflicts with the spec’s emphasis on simplicity & consistency. Checked JSON:API — Extensions and Profiles for reference. Also checked what is cloud computing, where different data fields update at different times.
Is this something already explored through meta / extension usage in practice? Would this kind of fine-grained expiry violate the spirit of JSON:API, or could it be proposed as an optional extension?
I would love to hear your thoughts or see if others have solved this problem differently.
Thank you !!